All Games

This is a tactic often confused and compared with infantry rushing, and its also one of my favorite tactics to use. This involves using APC's of one sort or another to send a lot of infantry to an enemy position, and then use the APC's to support the infantry in an assault. This is different from infantry rushing because the latter utilizes simply hordes of infantry while the former uses smaller, more mobile and better protected groups of infantry. It is a relatively cheap attack as well when compared to building hordes of tanks or making superweapons. One problem with this involves the APC's themselves. In all the C&C games, APC's are relatively poorly armed to fight armored tanks, especially the Flak Track, so that the infantry must generally fight armored vehicles on their own, leaving the transports to tackle enemy infantry. APC's are also typically not very well armored, leaving the infantry vulnerable. The APC's in Tiberian Dawn and Red Alert at least have decent armor, but personnel carriers from other games are far less endowed. The IFV has relatively powerful armament, but it can only carry one unit, so the Allies must either build lots of IFV's or use Nighthawk helicopters, which are poorly armed and armored like other APC's. Since GI's are slower than their Soviet counterparts anyway, the Allies have a real problem with any kind of infantry assault, forcing them to use their weaker, less-armored tanks against the Soviets. When used right, and especially when supported by tanks, this tactic can easily win a battle. The problem is that it requires more skill and finesse then most would guess. This is most effective with at least 2 "divisions" flanking on different sides of an enemy base. Newbies using this strategy can be crushed, but veterans can use it more effectively.

Mechanized Specialties

This is a strategy similar yet different from mechanized infantry. Similar in that you use APC's to get infantry somewhere, different in the way you do it and the units you use. The most common example is using an APC (especially the stealth Atreides APC) to sneak in a few engineers past enemy defenses and capture some vehicles. SEALS, Snipers, and Yuri's are also commonly used. This is a tactic which can rarely win a battle, but can often turn the tide of it. It is expensive and risky to do however, especially with non-stealth APC's, and requires much micromanagement to successfully sneak past enemy lines. Many online try this tactic without taking the time to micromanage it, and they thus give it up. Used effectively, however, it can cripple a base for primary assault. I'm sure there are many, many other tactics that are not listed here. These, however, are probably the most common. So, which do I use, you may ask. The "perfect attack" does not exist. The one that comes closest (and, ironically, is almost never seen), is probably the "combined arms" attack. This utilizes tanks, infantry, APC's, aircraft, super weapons, and naval weapons in a grouped effort. Of course, this is phenomenally expensive to do and requires a lot of management and time. A combined arms player can be thwarted by a mere early tank rush.

The problem with most of these tactics is that people don't realize that you need to have support as well. A horde of tanks can be slaughtered by well-entrenched infantry, but add a few Flak Tracks and the group can wipe out the enemy. Mechanized infantry can be thwarted by tanks, but a few tank destroyers or some air support can help the infantry seize the day.
There is no one tactic you should use necessarily. You must find one that fits your style and skill at playing. Still, I'll try and list here the most effective tactics in order: